The present invention relates to a method and improved apparatus for separating a distillate resulting from distillation to produce essential oils. More specifically, the present invention relates to a low-flow separation process including an improved apparatus.
Essential oils are aromatic materials of vegetable origin and are typically used to create perfumes, soaps, lotions, and flavorings. Essential oils occur in many different parts of plants; for example, in the roots (e.g. vetiver), bark (e.g. cinnamon), heartwood (e.g. sandalwood), leaves (e.g. bay), herbs (e.g. peppermint), seeds (e.g. nutmeg), and flowers (e.g. lavender).
The essential oil of a plant consists of many compounds, which generally boil between 150-degrees C. to about 300-degrees C. If attempts are made to remove these compounds by dry distillation many will decompose and the oil will be ruined. However, the compounds are steam volatile and can be distilled out of the vegetal materials at around 100° C. Thus, the majority of essential oils are produced by the process of steam distillation, water/steam distillation, or hydro-distillation.
Preparation of the plant material for distillation varies: Some material must be distilled immediately after harvesting, whereas other is stored for a day or two before distilling, and yet other material can be stored indefinitely before distillation. In general, flowers should be distilled immediately but herbaceous material benefits from wilting for one or two days before distillation. And, woody materials may need to be ground and/or soaked before distillation.
There are three basic types of essential oil distillation: Water (or hydro-distillation) distillation, water and steam (wet steam) distillation, and steam (or dry steam).
The first type, hydro-distillation, immerses the plant material in water (charge) are both boiled. As a result, hydro-distillation uses the simplest type of still and are commonly used by smaller-volume producers of essential oils. One disadvantage of this method and device revolves around the heat source used to boil the suspended plant material in water: The heat is difficult to control, which makes the rate of oil production variable, and more importantly, this technique can lead to local overheating and “burning” of the charge leading to a poorer quality oil.
Another form of hydro-distillation incorporates generating steam from a boiler that is separated from the still. The steam then heats an inner pot containing water and plant material. One disadvantage of this approach is that it requires the heating of a large quantity of water adding cost and time needed for each distillation. This method is generally used for delicate flowers such as rose petals and orange blossoms.
The second type, water/steam distillation, utilizes a still with a grid that suspends the plant material above the water level. The water is boiled below the charge and wet steam passes through the plant material. Thus, the plant material is protected from direct heat and contact with the water. One limitation of this method is extended distillation times.
The third type, steam distillation, utilizes steam provided from a separate boiler. The still contains a grid plate under which a steam spreader pipe is fitted. The advantages of this type of “not dry” steam distillation are that it is relatively rapid, therefore charging and emptying the still is much faster and energy consumption is lower. Steam distillation decreases distillation time and improves efficiency of the operation.
Regardless of the type of distilling, the next phase of collecting essential oils from plants involves condensers and separators. Accordingly, the steam containing essential oil vapor is directed out of the top of the still and into a condenser. The conventional art instructs that this extraction of heated steam and oil be by way of a gooseneck with a gauze or screen fitted at the mouth of the gooseneck to prevent plant material being blown over into the condenser.
In the condenser the vapors are cooled, and as they cool, the oils condense out, separating the essential oils from the distillate (a mixture of water and plant essence). The combined oil and hydrosol are then, according to conventional teaching, directed into a Florentine flask, in which they separate into two layers. The essential oil will generally be lighter than water, the oil floats to the surface and the hydrosol drains away.
The conventional teaching instructs that it is important that the oil separators should be large enough in volume to minimize turbulence because significant amounts of oil can be lost with the distillate water caused by turbidity if the oil is not allowed to separate completely. In addition, the temperature of the distillate may have an important bearing on the efficiency of separation of essential oil and water as well as the specific gravity of the essential oil. The optimum temperature for obtaining the best separation can be found by trial and error.
Further, the art instructs that condensers and separators should be constructed of materials that do not react with essential oils or water. Mild steel rusts and is not suitable. Copper has been used successfully for many years, however copper will dissolve in some essential oils and reacts negatively with some components of various essential oils such as Eucalyptus and Geranium, for example. The conventional wisdom instructs that stainless steel is the optimum material for stills, condensers, and separators as it is resistant and durable and readily cleaned. One drawback of stainless steel is its expense and difficulty in forming certain shapes.
Glass containers are often used for smaller amounts of oil but larger quantities are invariably stored in metal drums. Mild steel drums lined with epoxy resin are very popular for essential oils. Plastic containers, e.g. polythene, should not be used because the oil may be absorbed by the plastic resulting in contamination.